Answer: ICMP redirection is used to inform a host to update its routing table to send packets through a more efficient route for a given destination.

Trigger

When a host sends a packet to a destination, but the router identifies a better route through another router, it triggers the redirection process.

ICMP Redirection Message

The router sends an ICMP redirection message back to the host. This message includes the IP address of the new, preferred router (the better gateway) for sending packets to the specific destination.

Host Routing Table Update

Upon receiving the ICMP redirection message, the host updates its routing table to use the new gateway for future packets to that destination.

Subsequent Traffic

All subsequent traffic to that destination from the host will use the updated, more efficient route.

Conclusion

ICMP redirection is a network optimization technique that allows routers to instruct hosts to use more efficient routes, enhancing overall network efficiency and reducing latency. It’s part of the ICMP protocol, which plays a crucial role in managing and controlling internet protocol operations.